PVC switched digital communications networks such as e.g. ATM (Asynchronous Transfer Mode) networks are widely used for high-speed broadband data transport. In this type of networks, once a call is established, it will use generally the same route for the life, unless a physical link of the route becomes unavailable, in which case the call is rerouted. Various routing criteria are used for centrally provisioning communication sessions between users of such networks. Some of the currently used criteria are cost of the route, number of hops along a route and bandwidth load of the respective route.
Since a communication network has at its disposal limited resources (link bandwidth and node processing capacity) to ensure efficient data transmission, efficient use of the resources is an important requirement. When traffic demand increases, a network may become congested, resulting in degraded network performance. On the other hand, for proper operation, a network must be implemented so as to avoid congestion. The simplest solution obviously is to increase the capacity of the network; however this solution is generally undesirable for evident reasons of costs. Other less obvious solutions in support of efficient network operation consist in applying preventive measures, of which the main one is load balancing. Load balancing attempts to fairly distributing the traffic over all the links of the network to avoid a local congestion in particular resources and to better utilize the resources across the network.
Currently, the most common criteria for load balancing are based on determining an aggregated BW (aggregated over multiple hops) for each possible route for a call, and selecting the route with the lowest aggregated utilization for a new call. This is for example described in the U.S. Pat. No. 6,697,333 (Bawa et al.) entitled “Bandwidth load consideration in network route selection”, issued on Feb. 24, 2004 to Alcatel. The patent describes load balancing methods applicable to both new calls and existing connected calls, using bandwidth load as a selection criterion in addition to route cost and number of link hops in a route. Particularly, the method described in the patent selects the path (route) for a call from alternative paths having equal least cost, and then equal least number of link hops, a path having the less average bandwidth represented as an aggregate of bandwidth usage for each link hop.
The problem with this approach is that the users do not have any involvement in the routing of their calls. But, in order to successfully manage the traffic across a PVC switched digital network it is important not only to allocate sufficient bandwidth for each connection from the knowledge of the source characteristics and the network status, but also to take into account user-specified criteria. Such criteria may be the a user specified calls priority, that indicates the relative importance of calls in the network and ultimately the order in which calls can be eventually released or submitted to a degradation of their quality of service. Another criterion could for example be the service category of the calls, or combinations of the above criteria, applied in a specified order, or subsets of the above criteria, etc.
Thus, there remains a need to provide a route selection method that takes into consideration user-specified criteria.